Heat Treatment Furnaces

   Heat treating is a group of industrial and metalworking processes used to change a material's physical, and sometimes chemical, properties. Metallurgical applications are the most common. Many other materials, such as glass, are also subjected to heat treatments. Heat treatment is the process of heating or cooling a material to extreme temperatures to achieve a desired result such as hardening or softening. Annealing, case hardening, precipitation strengthening, tempering, and quenching are all heat treatment techniques.

     It is worth noting that, while the term "heat treatment" refers to processes in which heating and cooling are done intentionally to change properties, heating and cooling frequently occur incidentally during other manufacturing processes such as hot forming or welding. Heat treatment is the process of heating or cooling a material to extreme temperatures to achieve a desired result such as hardening or softening. Annealing, case hardening, precipitation strengthening, tempering, and quenching are all heat treatment techniques.

    Metallic materials have a microstructure made up of small crystals known as "grains" or crystallites. Heat treatment is an effective method for manipulating metal properties by controlling the rate of diffusion and cooling within the microstructure. During heat treatment, an alloy's properties can change due to two mechanisms.

    The crystal structure is made up of atoms arranged in a specific pattern known as a lattice. This rearrangement, known as allotropy or polymorphism, can occur several times at various temperatures for a given metal. Diffusion causes the atoms of the dissolved element to spread out, attempting to form a homogeneous distribution within the crystals of the base metal when it is soluble.

     The atoms of the dissolved constituents (solutes) may migrate out of the solution if the alloy is cooled to an insoluble state. This type of diffusion, known as precipitation, results in nucleation, which occurs when migrating atoms group together at grain boundaries. Most heat treatable alloys, unlike iron-based alloys, do not undergo ferrite.

   When quickly cooled, many metals and nonmetals undergo a martensite transformation. The atoms of the solute become trapped within the lattice when the crystal matrix changes to its low temperature arrangement.

  When some alloys, such as steel, are rapidly cooled, the martensite transformation hardens the metal, whereas in others, such as aluminum, the alloy softens.